Just a note while you wait for some CSS help - you can add the company name etc before or after the existing footer but you can not replace the footer without having your blog suspended

Current Terms of Service:

11. Attribution. Automattic reserves the right to display attribution links such as ‘Blog at WordPress.com,’ theme author, and font attribution in your blog footer or toolbar. Footer credits and the WordPress.com toolbar may not be altered or removed regardless of upgrades purchased.

May I remove the ‘Blog at WordPress.com’ credit in my site’s footer?
Although the Custom Design Upgrade certainly grants you the capability to hide the credit from your site’s footer, you are not permitted to do so. Even our VIP bloggers are required to maintain the credit.

But I can't avoid the temptation (sorry Mike)! If you wish, you can now use CSS to make the font of the text you added identical to that of the credits, and/or remove the border below it, shorten the distances and unify the background color so that your text will look as if it's in the same area with the credits.

When I had my .ORG install I struggled with CSS and changed the font colors to a color that was easier to read - there was a reason when I moved over here I ask about Themes with built in large type and easy to read colors

With a self-hosted site, you can create a child theme and then edit the footer php script file and edit the footer content as you desire. Creating a child theme means that your changes would not be overwritten by future theme updates. You can find more information on creating a child theme in the WordPress.org Documentation.